Golf ball location system

ABSTRACT

A golf ball and golf ball search receiver is described. The golf ball includes a transmitter and the search receiver includes a receiver. The golf ball may be activated by an accelerometer that causes the transmitter to produce an RF signal across a predetermined frequency band for a duration of time, which may be determined by a timer. The transmitter modulates an audio signal and transmits the modulated signal within an output band of the transmitter. The receiver tunes to a narrower band thereby receiving and demodulating a fraction of the transmitted signal. The receiver&#39;s input band halves an input bandwidth set to coincide with a fraction of the output band, thereby alleviating adverse effects due to variations in transmitter and receiver components, as well as adverse effects due to localized noise within the output band. Additionally, relative positioning of the receiver&#39;s input band may cycle across the transmitter&#39;s output band to further mitigate the adverse effects of localized noise.

BACKGROUND

Attempts to successfully manufacture and market a golf ball having anembedded radio transmitter for radio location of a lost ball have beenunsuccessful. The lack of success may be due to the severe conditionsunder which golf balls are traditionally made (high pressures andtemperatures), and the severe conditions golf balls endure during play(high impact G-forces). The production of radio transmitters havingclosely controlled and stable center frequencies that remain stableunder ball construction and play conditions may be extremely difficult.

Golf balls containing sensors to trigger radio frequency transmittersmay be useful in the game of golf, as a lost ball constitutes a penaltyin score, as well as the obvious loss of the ball itself. Golf ballsthat emit radio signals for a few minutes after being struck can belocated with a simple radio receiver. The integration of a radiotransmitter with precise frequency control into a golf ball iscomplicated by the extreme shock balls encounter during play. Such harshconditions make the use of accurate but fragile components problematic.

A radio embedded in a golf ball may use either a quartz crystal or afree running oscillator to accurately generate and control the golfball's transmitter center frequency. Incorporation of a quartz crystaloscillator into a golf ball may be unfavorable from both cost anddurability points of view. Crystals typically represent a sizableportion of the cost of the circuits that employ them. Additionally,crystals are very susceptible to damage from impact forces such as thoseapplied to golf balls during manufacturing and normal use. Solutions toprotect a crystal from damage (e.g., insulating circuitry from shockforces) may reduce the probability of potential damage but may alsosignificantly increase the part and manufacturing costs of a golf ball.Furthermore, the cost of a high-reliability quartz crystal oscillatorthat is able to withstand the shock experienced during play may becost-prohibitive.

Therefore, it may be desired to have a durable, interference resilienttransmission and detection system contained within a golf ball. Further,it may be desirable to operate such a system with a free-runningoscillator.

SUMMARY OF THE INVENTION

Embodiments of the present invention relate to a golf ball and a golfball location system that assists in the recovery of golf balls lostduring a game of golf. The golf ball may include a transmitter circuitcapable of transmitting within a determined bandwidth, a bandwidth thatis wide enough to negate frequency drift of various transmittercomponents. In some embodiments, a transmitter modulates a signal at anaudible rate.

The location system may include a receiver circuit capable of receivinga signal at or near a designed center frequency. In some embodiments, areceiver has an input bandwidth that is narrower than the transmitter'soutput bandwidth. In some embodiments, a receiver has an input band thattraverses a wider band at a sub-audible rate.

In accordance with embodiments of the present invention, a system forlocating a golf ball comprises: the golf ball having an encapsulatedtransmitter that modulates an audible signal to an output band, whereinthe output band defines an output bandwidth; and a receiver having aninput band defining an input bandwidth wherein a center frequency of theinput band of the receiver is variable; wherein the input bandwidth issmaller than the output bandwidth.

In accordance with some embodiments of the present invention, a golfball comprises: an encapsulated transmitter that modulates an audiblesignal to an output band; wherein the output band defines an outputbandwidth and the transmitter includes a free running oscillator havingan inductor and a capacitor.

In accordance with other embodiments of the present invention, a methodto locate a golf ball using a golf ball location system having atransmitter encapsulated in a golf ball and a receiver, the methodcomprises: modulating an audible signal with the transmitter;transmitting the modulated signal to an output band; providing areceiver with an input band, wherein the input band is narrower andwithin the output band; receiving an input signal residing within theinput band; and varying a center frequency of the input band to traversethe output band.

In some embodiments of the present invention, a state of the powersource or battery of the golf ball is communicated by the golf ball.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a cutaway perspective view of a golf ball containing anencapsulated transmitter, in accordance with embodiments of the presentinvention.

FIGS. 2A through 2D graphically relate frequency tolerances andbandwidths of a transmitter and receiver, in accordance with embodimentsof the present invention.

FIGS. 3A and 3B relate a transmitter's output band to an examplemodulation waveform, in accordance with embodiments of the presentinvention.

FIGS. 4A through 4C relate a transmitter's output band to a receiver'sinput band and an example modulation waveform, in accordance withembodiments of the present invention.

FIGS. 5A and 5B show block and schematic diagrams of a transmitter inaccordance with embodiments of the present invention.

FIG. 6 shows a schematic diagram of an embodiment of a receiver inaccordance with the present invention.

FIG. 7 shows a plan view of a printed circuit board (PCB) having anetched inductor in accordance with embodiments of the present invention.

FIG. 8 shows a cross sectional view of a PCB according to someembodiments of the present invention.

FIG. 9 shows a perspective view of transmitter module to be encapsulatedwithin the core of a golf ball in accordance with embodiments of thepresent invention.

DESCRIPTION OF INVENTION

It is well-known that many golf balls are lost during play when golfballs land in particularly overgrown areas of a golf course. The losscan occur even though the ball may have been visible during its entireflight and the approximate region of the landing of the ball is known.The loss of a golf ball not only entails financial loss to the player italso means that the player is put at a disadvantage as far as gamescoring is concerned. The present invention aids in reducing theoccurrence of lost golf balls. Players employing golf balls that can bemore readily recovered are at an advantage both financially and byavoiding unnecessary point loss.

To provide a locatable golf ball, a free running oscillator having aninductor and a capacitor to set a transmitter's center radio frequencymay be used. Free running oscillators, however, may suffer fromexcessive tolerance problems. Some free running oscillators areconstructed from tank circuits having a capacitor and an inductor placedin parallel. Cost effective capacitors have a wide range of acceptabletolerances in the order of ±5%. Etched inductors similarly have a widerange of acceptable tolerances in the range of ±2% due to variables ofetching. Wire wound coil inductors have an even wider range ofacceptable tolerances.

To improve accuracy, some components are tunable. Etched inductors mayutilize various tuning methods, such as, e.g., using a conductive diskor a “tuning slug”. Tuning slugs, however, may be large, expensive andsuffer the disadvantage of potentially being disturbed during subsequentencapsulation. Tunable free running oscillators typically requirecareful adjustment prior to encapsulation and final ball molding. Evenafter careful adjustment, components may drift due to the pressures andtemperatures of final manufacturing and molding, and due to the ultimateabuse of play. Under such conditions a circuit may have an ultimateoperating frequency that can easily drift by several percent from itsfactory set frequency. These variations may be far outside the normalmodulation input bandwidths of traditional receivers.

One solution to combat the variations of free running oscillators is touse a transmitter that masks the variations by transmitting over a widefrequency bandwidth. Such a transmitter may have an output bandwidththat is substantially larger the potential frequency variation of theoscillator. A receiver may be designed to operate over a similarsubstantially wide or wider bandwidth. In such designs, even if theoutput band of the transmitter and the input band of the receiver do notexactly align, a majority of the transmitter's output bandwidth fallwithin the receiver's input band.

Unfortunately, such receivers, which have an input bandwidth nearlyequal to or greater than the transmitter's output bandwidth, leave thereceiver open to interference from any strong signal that falls withinthe receiver's input band. Furthermore, wide band transmitters typicallyuse more power than their narrower band counterparts.

FIG. 1 shows a cutaway view of a golf ball 10 containing an encapsulatedtransmitter region 20. The encapsulated transmitter 20 is surrounded bymolded rubber 30 that is enclosed by a molded cover 40. A transmitter100 within the encapsulated transmitter region 20 is positioned withinthe golf ball 10 during the manufacturing process. Rather than includinga transmitter employing a fragile crystal, embodiments of the presentinvention may use an inexpensive inductive-capacitive (LC) tank circuit,which resonates at or near a desired carrier frequency. By eliminatingthe crystal, the golf ball 10 may have improved resiliency againstimpact damage and shock absorbing packaging may be reduced or omitted.

According to some embodiments of the present invention, even if thecenter frequencies of a transmitter and a receiver have drifted fromtheir designed center frequencies, for example, due to manufacturingvariations, environmental conditions and/or normal wear, thetransmitter-receiver pair utilizes a modulation technique to overcomethese frequency uncertainties. A transmitter 100 transmits within a wideband and a complementary receiver has an input bandwidth that isnarrower than the transmitter's output bandwidth.

Some embodiments include a golf ball having a transmitter that modulatesa signal having audible frequencies. The transmitter modulates thesignal having audible frequencies across the transmitter's output band.Frequencies between 20 Hz and 20 kHz are called the audible frequencies.A signal having an audible repetition rate includes periodic signalsthat repeat at an audible frequency. A signal having an audiblerepetition rate forms a signal having audible frequencies. A periodicsignal having an audible repetition rate between 20 Hz and 20 kHzrepeats every 50 microseconds to 50 milliseconds. For example, a signalmay be a gradually rising or falling saw-tooth waveform repeating at anaudible rate between 20 Hz and 20 kHz, thereby repeating every 50microseconds to 50 milliseconds. Alternatively, a signal having audiblefrequencies may be formed by a signal having a changing frequency. Forexample, the signal may be a waveform having a center frequency thatchanges by incrementally increasing and/or decreasing its centerfrequency among a set of values between 20 Hz and 20 kHz.

In some embodiments, a transmitter's output band is greater in spectralwidth than the receiver's input band. For example, the transmitter'soutput band may span several MHz and the receiver's input band may spanseveral hundred kHz. By using a receiver with a front-end having anarrower bandwidth that the full transmitter's bandwidth, a receiver maysubstantially decrease the probability that it receives unwanted signalsthat interfere with proper detection of a golf ball's transmittedsignal.

In some embodiments, the receiver's input bandwidth represents between 2and 8 percent of the transmitter's output bandwidth. For example, atransmitter may have an output bandwidth between 4 MHz to 5 MHz and acorresponding receiver may have an input bandwidth between 100 KHz to300 KHz. In some embodiments, the receiver's input bandwidth representsless than 50 percent of the transmitter's output bandwidth. In someembodiments, the receiver's input bandwidth represents between 5 and 20percent of the transmitter's output bandwidth. In some embodiments, thereceiver's input bandwidth is less than 5 percent. In other embodiments,the receiver's input bandwidth is greater than 50 percent of thetransmitter's output bandwidth.

In some embodiments, a detection unit includes a receiver that has astationary input band or input window. In other embodiments, thereceiver has an input window that traverses at least a part of thetransmitter's output band at a sub-audible rate. By sweeping areceiver's input band across a transmitter's wider output band, areceiver is not permanently impaired by a stationary interfering signal.As a result, precise frequency alignment between the transmitter andreceiver is not necessary when using the present invention.

A sub-audible rate is a rate between 0 Hz and 20 Hz. For example, a 20Hz input window, which traverses a spectrum at a sub-audible rate of 20Hz, traverses the spectrum every 50 milliseconds. An input window thattraverses a spectrum at 0.5 Hz cycles through a spectrum every 2seconds.

In some embodiments, a receiver traverses its input window using aperiodic waveform, e.g., a saw-tooth or triangular waveform. In someembodiments, a receiver traverses its input window with a periodicwaveform having a period greater than or equal to approximately 50milliseconds, such as a period set between 50 milliseconds and 10seconds, or more particularly between 200 milliseconds and 5 seconds, oreven more particularly, between one-half second and 2 seconds.

In some embodiments, the receiver has an input window that traverses theentire designed output band of a transmitter. In other embodiments, thereceiver has an input window that is a fraction as wide as thetransmitter's output band and traverses only a portion of the designedoutput band of a transmitter. The portions of the transmitter's outputband that the receiver does not traverse form a guard band, which isused to insure that the receiver's window falls within the transmitter'soutput window. A larger guard band allows a design to use componentswith wider tolerances and allows for drifts in component values overtime and use.

For example, a transmitter is designed with an output band that is 5 MHzwide. A corresponding receiver traverses its input window across only 2to 3 MHz of the entire 5 MHz bandwidth of the transmitter. A receiverhaving an input window that is 300 kHz wide receives a signal from atransmitter that has a transmission band that is 5 MHz wide. Thereceiver may slide its input window across just the center 3 MHz of the5 MHz wide transmission window. This receiver may traverse its inputwindow across the 3 MHz sub-window once every second or equivalently ata sub-audible rate of 1 Hz. This design forms a 1 MHz guard band at eachend of the transmitter's output window. The guard band allows forsubstantial drift in component values.

Some embodiments include both a golf ball that modulates an audible ratesignal and a detection unit having an input window that traverse a bandat a sub-audible rate. The golf ball includes a transmitter thatmodulates an audible signal to an output band. The detection unitincludes a receiver that has an input window that traverses at least aportion of the transmitter's output band periodically at a sub-audiblerate.

In some embodiments, the ratio between the audible repetition rate ofthe periodic signal and the sub-audible rate at which the receiver'sinput window traverses the transmitter's output window is set to a valuebetween 20000-to-1 and 10-to-1, or more particularly between 2000-to-1and 50-to-1, or even more particularly between 400-to-1 and 100-to-1.

In some embodiments, once activated, a golf ball 10 transmits a signalthat sweeps between two frequencies about the actual center frequency ofthe golf ball. The transmitted signal sweeps across a transmit band. Ifa receiver has a narrower bandwidth than the transmitter, thetransmitter will eventually transmit a signal that passes through thenarrower input band of the receiver.

In some embodiments, prior to encapsulating the transmitter 100, thetransmitter 100 is adjusted to transmit with a predetermined centerfrequency by modifying the inductor's inductance. Etch inductors may betuned using conductive disks. Coil inductors may be tuned by bending thecoil turns. Once tuned, the inductor may be encapsulated.

The frequency modulation bandwidth of the transmitter may be designedwide enough to account for: (1) the transmitter's expected maximumcenter frequency deviation during molding, temperature and service; (2)the expected maximum receiver frequency tolerance; and (3) the width ofthe input band of the receiver.

In some embodiments, a receiver used to detect a golf ball may use areceiver having at a fixed center frequency. In other embodiments, areceiver has a varying center frequency. The varying center frequencymay oscillate between an upper bound and a lower bound at a sub-audiblerate, e.g. 1 Hz or 2 Hz. A window, which represents the input band ofthe receiver, thereby cycles across the output band of the transmitterat the sub-audible rate. Embodiments that sweep or cycle the inputwindow of the receiver across the output band of the receiver help toreduce the adverse effects of interfering signals and also reduce theneed for well tuned components in both the transmitter and receiver.

FIGS. 2A through 2D graphically relate center frequency tolerances tooutput bandwidth BW_(Tx) and input bandwidth BW_(Rx) of the transmitter100 and receiver, respectively. Both the transmitter 100 and receiverare designed to work at a center frequency off_(C)=f_(designTxC)=f_(designRxC). FIG. 2A shows a designed centerfrequency f_(designTxC) of a transmitter 100 may vary within a tolerancefrom a low of f_(designTxC) _(—) _(Low) to a high of f_(designTxC) _(—)_(High). Drift and variations in a transmitter's center frequency aredue to several factors, including component tolerances, manufacturingconditions, usual ball wear, and operating conditions.

FIG. 2B illustrates an output band of a transmitter 100. The transmitter100 has a transmit bandwidth BW_(Tx) that is centered on f_(actualTxC).The actual transmitter output band low and high frequency limits aref_(actualTxLow) and f_(actualTxHigh), respectively. The output bandwidthBW_(Tx) is the difference between f_(TxActualHigh) and f_(TxActualLow):BW_(Tx)=f_(TxActualHigh)−f_(TxActualLow). A transmitter may emit asignal anywhere within its output bandwidth.

FIG. 2C shows a center frequency of a receiver may vary from a low off_(designRxC) _(—) _(Low) to a high of f_(desighRxC) _(—) _(High).Again, the drift and variations may be due several factors, includingcomponent tolerances, manufacturing conditions and operating conditions.

FIG. 2D illustrates an input band determined by design of a receiver.The receiver has an input bandwidth BW_(Rx) that is centered onf_(actualRxC). The actual receiver input band low and high frequencylimits are f_(actualRxLow) and f_(actualRxHigh), respectively. The inputbandwidth BW_(Rx) is the difference between f_(RxActualHigh) andf_(RxActualLow): BW_(Rx)=f_(RxActualHigh)−f_(RxActualLow). A receivermay detect signals anywhere within its input bandwidth.

A transmitter 100 is designed to transmit at a center frequency off_(designTxC) but in fact has an actual transmitter center frequencyf_(actualTxC), which falls anywhere between f_(designTxC) _(—) _(Low)and f_(designTxC) _(—) _(High). Similarly, a receiver is designed toreceive at a center frequency of f_(designRxC)=f_(designTxC) but in factmay have an actual receiver center frequency f_(actualRxC), which fallsanywhere between f_(actualRxLow) and f_(actualRxHigh) and may bedifferent from the actual transmitter center frequency.

In operation, a receiver's input band may be designed to fall entirelywithin a transmitter's output band even when the center frequency of thetransmitter 100 has drifted. For example, a transmitter 100 may have acenter frequency that has drifted in one direction and the receiver mayhave a center frequency that has drifted in the other direction. Toselect an appropriate transmitter output bandwidth BW_(Tx) knowing thatcenter frequency variations are possible, one may consider the worstcase frequency drifts along with a predetermined receiver inputbandwidth BW_(Rx). The worst scenarios occur when the transmitter 100and receiver have center frequencies that drift to extremes in oppositedirections. However, even when a portion of the receiver's input bandfalls outside of the transmitter's output band, the signal from thetransmitter may still be detectable.

The lower boundary of the output band f_(actualTxLow) of the transmitter100 may be determined by assuming the transmitter 100 has an actualcenter frequency f_(actualTxC) that has drifted up to an extreme centerfrequency f_(designTxC) _(—) _(High) and the receiver has an actualcenter frequency f_(actualRxC) that has drifted down to an extremecenter frequency f_(designRxC) _(—) _(Low). The spectral distancebetween the transmitter's actual center frequency f_(actualTxC) and thereceiver's actual center frequency f_(actualRxC) is:(f_(actualTxC)−f_(actualRxC)), and in this extreme case is(f_(designTxC) _(—) _(High)−f_(designRxC) _(—) _(Low)). The lowerboundary of the output band f_(actualTxLow) is equal to thetransmitter's actual center frequency less this spectral distance lesshalf the width of the receiver's input bandwidth:f_(actualTxLow)={f_(actualTxC)−(f_(designTxC) _(—) _(High)−f_(designRxC)_(—) _(Low))−0.5*(BW_(Rx))}.

Similarly, the upper boundary of the output band f_(actualTxHigh) of thetransmitter 100 may be determined by assuming the transmitter 100 has anactual center frequency f_(actualTxC) that has drifted down to the otherextreme center frequency f_(designTxC) _(—) _(Low) and the receiver hasan actual center frequency f_(actualRxC) that has drifted up to anopposite extreme center frequency f_(designRxC) _(—) _(High). Thespectral distance between the transmitter's actual center frequencyf_(actualTxC) and the receiver's actual center frequency f_(actualRxC)is: (f_(actualRxC)−f_(actualTxC)), and in this extreme case is(f_(designRxC) _(—) _(High)−f_(designTxC) _(—) _(Low)). The upperboundary of the output band f_(actualTxHigh) is equal to thetransmitter's actual center frequency plus this spectral distance plushalf the width of the receiver's input bandwidth:f_(actualTxHigh)={f_(actualTxC)+(f_(designRxC) _(—)_(High)−f_(designTxC) _(—) _(Low))+0.5*(BW_(Rx))}.

The lower and upper boundary thereby defined the transmitter's outputbandwidth: BW_(Tx)=(f_(actualTxHigh)−f_(actualTxLow)), which equals[{f_(actualTxC)+(f_(designRxC) _(—) _(High)−f_(designTxC) _(—)_(Low))+0.5 (BW_(Rx))}−{f_(actualTxC)−(f_(designTxC) _(—)_(High)−f_(designRxC) _(—) _(Low))−0.5*(BW_(Rx))}], which simplifies to[(f_(designTxC) _(—) _(High)−f_(designTxC) _(—) _(Low))+(f_(designRxC)_(—) _(High)−f_(designRxC) _(—) _(Low))+BW_(Rx)], or equivalently to thevariation in the transmitter plus the variation in the receiver plus thereceiver's input bandwidth.

If a transmitted signal sweeps across the full transmit modulationbandwidth of the transmitter, that is from f_(actualTxLow) tof_(actualTxHigh), a receiver having a narrower input band that fallswithin the transmitter's output band will periodically receive thetransmitted signal.

FIGS. 3A and 3B relate a transmitter's output band to an examplemodulation waveform. FIG. 3A shows a transmitter's output transmissionband having a bandwidth of BW_(Tx). FIG. 3B shows one possiblemodulation waveform of a transmitter 100. As time progresses, themodulation waveform, shown as a saw-tooth wave, is modulated byfrequency modulation (FM). As the saw-tooth wave value increases from aminimum value to a maximum valve, the FM transmitter generates a peakthat sweeps from frequency f_(actualTxLow) to frequencyf_(actual TX High). Once the maximum value is reached, the processrepeats again starting from the minimum value.

For example, a signal having frequency f₁ is transmitted at time t₁. Astime progresses from t₁ to t₂, the frequency of the transmitted signalprogresses from f₁ to f₂. An ever increasing frequency is transmitteduntil the upper end of the transmitter's output band is reached. Oncethe saw-tooth wave reaches its maximum value and returns to its minimumvalve, the FM transmitter effectively generates a signal that restartsfrom a frequency f_(actualTxLow). The cycle of generating an increasingthen resetting frequency signal continues as long as the saw-toothmodulation signal persists.

FIGS. 4A through 4C relate a transmitter's output band to a receiver'sinput band and provide an example modulation waveform. FIG. 4A shows atransmitter's output band having a bandwidth of BW_(TX). FIG. 4B shows areceiver's input band having a narrower bandwidth of BW_(RX) that fallswithin the transmitter's output band. FIG. 4C shows ranges of time whena receiver detects a transmitted signal within its input band. Thereceiver receives a passing peak of energy as the transmitted signalsweeps through the receiver's input band. Two durations of time duringwhich the receiver detects the transmitted waveform are shown. The firstduration occurs as the signal generated by the transmitter 100 sweepsbetween f_(actualTxLow) and f_(actualTxHigh). During this period thefrequency transmitted falls within the actual receiver input band. Thesecond duration occurs as the transmitter resets and sweeps again.During these durations of time, the receiver detects the transmittedsignal.

In the example illustrated, the transmitter modulates a saw-toothsignal. Additionally, the center frequencies of the transmitter andreceiver may be slightly skewed. The resulting demodulated signal, whenconverted to an audible signal, may be masked by the monotonic nature ofthe saw-tooth waveform.

Alternatively, the transmitter could modulate a triangular signal. Ifthe center frequencies of the transmitter and receiver are slightlyskewed, the resulting demodulated signal, when converted to an audibleor visual signal, may be perceived as a series of double bursts. Bycomparing the elapsed time between the double bursts and betweensuccessive sets of double bursts, one can determine the aggregate driftbetween the transmitter and receiver center frequencies.

The saw-tooth waveform shown in FIGS. 3B and 4C may be replaced by anynumber of modulation waveforms. A monotonic waveform that simplyincreases from frequency f_(actualTxLow) to frequency f_(actualTxHigh)then restarts increasing from frequency f_(actualTxLow) again, such asthe saw-tooth waveform, would also mask the effects of drift anddifferences between the transmitter and receiver center frequencies.Alternatively, a sinusoidal wave, triangular wave, a monotonicallyincreasing potentially periodic waveform or the like may be used.Alternatively, other periodic waveforms (having a repetition rate of,for example, 20 Hz to 20 kHz, or more particularly 60 Hz to 2 kHz) maybe used. The frequency of the modulation waveform may be intentionallyset to a low frequency but below the upper limit of the audio range.Modulated signals received by the receiver through the receiver's inputband are received at a rate within the audio frequency range. Anoperator can “home in” on the lost golf ball by listening for effects ofthe ball's modulation signal. A retractable antenna on the detector unitmay be used to adjust the receiver's gain during the homing process.

Many RF environments might have one or more interfering signals withinthe transmitter output band. If one of these interfering signals existswithin the receiver input band, a receiver might not be able to detect asignal from a transmitting golf ball. By varying the position of thereceiver's input band, a particular interfering signal may beperiodically avoided.

In some embodiments, the receiver center frequency varies within a bandof frequencies that may be centered on the designed transmitter centerfrequency. In some embodiments, the receiver center frequency variesperiodically at a sub-audible rate such that the position of thereceiver's input band appears to slide across the transmitter's outputband. The center frequency value may step among several predeterminedcenter frequency values. Alternatively, the center frequency may sweepor traverse across a range of frequencies. The range of frequencies thatthe center frequency varies within may be limited such that the receiverinput band always falls within a part of the transmitter's output band.By stepping or sweeping a receiver's center frequency at a sub-audiblerate, the input window of the receiver moves. An interfering signal maymomentarily interrupt reception while the receiver's input band capturesthe interfering signal. Once the input window moves past the interferingsignal, however, the receiver filters out and avoids the interferingsignal.

As shown in FIGS. 4A and 4B, the receive window (defined by the receiverbandwidth BW_(Rx)) is narrower than the transmit window (defined by thetransmitter bandwidth BW_(Tx)). Though the receiver bandwidth BW_(RX)might not substantially change, the placement of the receive window (orreceived input band) changes as the window follows the varying receivercenter frequency. By implementing a receiver with an input window thatsteps or sweeps across a transmitter's output band, component tolerancesmay be relaxed. Using components that have wider tolerances andcomponents that do not need tuning during the assembly process reducesthe manufacturing costs and decreases the effects of long term componentdegradation.

An embodiment having a varying receiver center frequency effectivelysteps or slides the receiver window up or down the spectrum within thetransmit window. In some embodiments, the receiver center frequencysteps or slides the input window of the receiver up or down the transmitband at a sub-audible rate, e.g., 1 or 2 Hz. In some embodiments, thereceive window passes across a majority of the transmitter's outputwindow during one sub-audible cycle. In some embodiments, a sub-audiblecycle follows a saw-tooth wave. For example, the input window starts atthe low end of the transmitter's output band and slowly steps or slidesup to the high end of the output band. Once the high end is reached, theinput window is repositioned at the low end to repeat the process.

In some embodiments, a receiver uses an FM demodulator. In otherembodiments, a receiver uses an AM demodulator. An AM demodulator hasthe advantage of being less expensive to implement than an FMdemodulator. Additionally, a receiver designed with intentionallyvarying center frequency may be more effectively implemented with an AMdemodulator than with an FM demodulator.

FIG. 5A shows a block diagram of an exemplary embodiment of atransmitter 100. The golf ball's transmitter 100 consists of a powersource (e.g., a battery) electrically attached to circuitry having anoscillator, sensor, modulator, modulation source, timer, and antenna.

The oscillator may be an LC tank circuit having an inductor L and acapacitor C. The LC tank circuit acts as a control component of thetransmitter and generates a resonant frequency that may be used as anoscillator whose frequency is controlled by individually tuning theinductor and/or the capacitor. The resonant frequency of the LC tankcircuit and the component values determine the actual center frequencyof the transmitter circuit. The resonant frequency may be tuned byadjusting either the circuit's inductance or capacitance by methods wellknown to those skilled in the art.

The inductor L may be, for example, either an etched inductor or a coilinductor. In some embodiments, the inductor is etched onto a printedcircuit board (PCB) thereby defining an inductive strip. An inductivestrip, such as a spiral inductive strip, may be tuned by placing one ormore conductive patches over the inductor trace on the PCB.Additionally, the inductive strip or coil inductor may double as anemitting antenna as shown in FIG. 5B. The inductor couples the resonantenergy from the tuned circuit to free space as propagatingelectromagnetic waves (radio waves). Furthermore, as the radiating areaof the inductor is necessarily small, its efficiency as the transmittermay be improved by operating the device at a rather high frequency, onthe order of hundreds of megahertz.

The transmitter's impact sensor may be any suitable sensor componenthaving the ability to indicate when a sufficient amount of force hasbeen placed on the golf ball. A sensor such as an accelerometer, shocksensor, force sensor, acceleration sensor or impact sensor may be usedto indicate when the golfer has struck the golf ball and thus the desirefor golf ball detection may be imminent. Alternatively, a usercontrollable switch may be used.

The timer and switch are used in tandem to control the ON-time of thetransmitter. For example, once the sensor detects sufficient force, suchas that placed on the golf ball during its launch, the timer closes theswitch to initiate transmission of an FM sweeping signal.

An integrated circuit (IC) may be used to combine multiple elements ofthe transmitter circuitry. For example, the FM modulator, modulationsource and timer functions may be integrated into a single IC chip. TheIC chip may be conveniently mounted onto the PCB holding the inductivestrip.

A battery, one or more accelerometers, a wide band FM radio transmitterand a timer may be integrated as a module 100 into the core of a golfball. In some embodiments, the accelerometer turns the transmitter on,and simultaneously starts the timer when sufficient shock is detected.Once the timer has expired, the circuitry turns the transmitter off. Thetimer may be set to expire after a sufficient time has passed that wouldallow a golfer to find a wayward ball, however, it may be desired thatthe time not be set to such a long duration that the power sourceprematurely exhausts. Three to five minutes may be an appropriate lengthof time for ball transmission.

In some embodiments, a carrier is modulated with a modulation waveformby altering the capacitance of the LC tank circuit.

FIG. 5B shows an LC tank circuit of a transmitter that is modulated byvarying the tank circuit's capacitance. The circuit forms an oscillatorcomprised of a bank of capacitors having a variable capacitance C₁, afixed capacitor having a capacitance C₂, and inductor having inductanceL. The bank of capacitors and the fixed capacitor combine to form atotal capacitance C=C₁+C₂. The bank of capacitors, which provide avariable capacitance, is placed in parallel with the tank circuit tomodify the circuit's total capacitance. The resulting resonant frequencyof the circuit is $\frac{1}{2\quad\pi\sqrt{LC}}.$

The bank of capacitors may be comprised of a number of capacitorsconfigured in parallel. As additional capacitance is desired, capacitorswith higher capacitances are switched into the circuit. Each capacitoris associated with a MOS switch that is configured to connect anddisconnect the capacitor to and from the circuit. An external controlsignal is used to open and close the MOS switch, thereby electricallydisconnecting and connecting the capacitor to the tank circuit. Adesired capacitance may be derived from a signal proportional to themodulated waveform. The resulting LC tank circuit thereby generates amodulate signal. If the modulation waveform varies between two extremes,the transmitted modulated carrier signal varies between an upper boundand a lower bound of the transmitter output band.

In some embodiments, a bank of capacitors is controlled by a digitalsignal supplied by an up/down counter. For example, a counter countsfrom a low valve to a high value, then down to the low value again. Byrepeating this pattern, a saw-tooth waveform may be formed. In someembodiments, the pattern repeats at an audible rate.

Some embodiments include a transmitter having a desired transmitteroutput bandwidth of 5 MHz at a desired center frequency of 226.25 MHz.The transmitter includes an inductor L of 22 nH and a fixed capacitor of20 pF in parallel with a bank of capacitors that provides from 2 pF to 3pF of capacitance. The bank of capacitors has a 9-bit control input,thereby allowing the capacitance to be controlled in steps of 2⁻⁹ pF. A9-bit control input may be used to individually switch in and out anyone of 512 capacitors. These component values resulted in an output bandthat covers approximately 223.7 to 228.8 MHz. A clock stepping theup/down counter at 25 kHz causes the total capacitance to vary from 22pF to 23 pF, then back down to 22 pF in 100 μsec or equivalently at anaudible rate of 10 kHz.

In some embodiments, the user may manually “tune” the detection unit.Manual tuning adjusts the receiver's center frequency slightly higher orlower such that the user may search for a clean spot on the spectrumwith no substantial interference. Once the receiver is tuned to a quietrange within the band, the user may more easily detect the golf ball'stransmitted signal. This allows the user to operate a receiver in a bandthat is absent significant interference when searching for the ball'stransmitted signal.

The modulated signal produced by the ball can be characteristic, so thatthe ball's signal can be identified in the presence of interferingnoise. In some embodiments, the modulation signal is a sequence ofaudible notes. For example, a transmitter transmits a sequence of notesuntil the timer 100 expires. The sequence of notes may repeat at a rateof approximately 3 cycles per second. One possible sequence may be a 440Hz tone followed by a 660 Hz tone followed by an 880 Hz tone. Otherpossible signals include a continuous 5 kHz tone and a sequence of 5 kHztones.

In some embodiments, a transmitter 100 periodically incorporates a pausein its transmission to aid in prolonging a golf ball's power supply. Forexample, if the golf ball, when active, transmitted with an ON-OFF dutycycle of 1:5, a golf ball's battery could be extended substantially. Insuch a system, when a ball has been detected, the receiver maydemodulate a series of audible tones followed by a pause. The pauses,which occur between the series of audible tones, last five times as longas the audible tones last if the duty cycle is 1:5.

As a further advantage in some embodiments, a transmitter 100 has theability to communicate a signal indicative of the energy remaining inthe transmitter's power supply. The transmitter may transmit analternate pattern if the power supply's remaining energy or voltage islow or lower than a threshold. For example, a unique sequence, such as a440 Hz tone followed by a 660 Hz tone, could be repeated to indicatethat a golf ball's battery is substantially low. Alternatively, the rateat which the tones change from one tone to the next tone may be used toindicate the golf balls battery condition. For example, the sequence mayrepeat at a rate of 1 cycle per second, rather than 3 cycles per second,when the battery is low.

FIG. 6 shows a block diagram of a receiver. The receiver may include anantenna, RF amplifier, mixer, sub-audible wave modulator, oscillator,intermediate frequency amplifier (IF amp) and detector circuit, audioamplifier, and indicator. In some embodiments, the receiver uses an AMdemodulator the. In other embodiments, receiver uses an FM demodulator.In some embodiments, the antenna is a retractable antenna therebyadjusting the receiver's gain when the antenna is extracted orcollapsed.

The RF amplifier receives a signal from the antenna and provides asignal to the first input of a mixer. The mixer receives a second inputfrom an oscillator. In some embodiments, the oscillator is a variableoscillator. The frequency produced by the oscillator is varied at asub-audible rate by a signal provided by a sub-audible wave modulator.The sub-audible wave modulator may be formed with a varactor (also knownas a variable capacitance diode or a varicap). The varactor provides anelectrically controllable capacitance, which may be used in adjust thefrequency of the oscillator at a sub-audible rate. By varying the secondinput into the mixer, the input window of the receiver effectively movedacross a band at a sub-audible rate.

The mixer produces an intermediate frequency signal, which is amplifiedand detected by the IF amp and detector circuit. The detector circuitmay be a logarithmic amplitude detector. The signal from the detectormay be amplified and provided to an indicator, such as a speaker, an LEDor the like. An optional audio amplifier may be used to amplify thedetected signal prior to providing the signal to the indicator.

Radio location by homing in on a transmitter while listening for audiblesignal strength may be very difficult using a traditional FM receiverhaving a front-end limiting stage. A limiting-stage automaticallyadjusts the amplitude of the received signal. If a limiting stage isused, the audible signal strength does not appreciably vary as thereceiver approaches the transmitter. The receiver used in this inventioncan benefit by replacing the limiting stage with a user-controlled,variable gain stage prior to the detector allowing the user to adjustthe receiver's sensitivity and overall receiver loudness. Alternatively,the antenna may be a retractable antenna. The gain of the receiver maybe adjusted by adjusting the length of the antenna. In addition, anoperator's hand may cup the detection unit, thereby reducing the overalleffectiveness of the antenna. As an operator nears the transmittingball, retracting and/or cupping of the antenna reduces the gain of theantenna, thereby allowing an operator to detect a golf ball residingwithin a very short radius.

FIG. 7 shows a plan view of a printed circuit board (PCB) having anetched inductor in accordance with the present invention. The inductoris connected by vias (or through holes) to the component side of thePCB. Also shown is a metallic sticker that may be attached with aninsulating adhesive to the etched inductor to tune or alter theinductor's inductance. Alternatively, the etched inductor may bereplaced with a coil of wire having a small number of turns. Some coilinductors have as few as two to three turns with a small diameter, suchas 8 millimeters. The coil's inductance may be tuned by bending the coilturns prior to encapsulation.

In the production of the golf ball core circuitry, an assembled printedcircuit board, attached to its battery, may be allowed to transmit whilethe natural frequency of the assembled LC tank circuit is measured.Component values for the capacitor and for the etched inductor may beintentionally chosen such that the LC tank circuit resonates at afrequency that is slightly lower than the intended frequency ofoperation.

FIGS. 8 and 9 show views of a printed circuit board (PCB). FIG. 8 showsa cross sectional view of a PCB according to some embodiments of thepresent invention. FIG. 9 shows a prospective view of an embodiment of atransmitter 100 including its PCB electrically connected to a battery.The etched inductor may face away from the battery to aid in efficientradiation of the transmitted signal.

Examples provided are meant to be exemplary and not limiting. Thefollowing claims define the scope and limits of the invention.

1. A system for locating a golf ball, the system comprising: the golfball having an encapsulated transmitter that modulates an audible signalto an output band, wherein the output band defines an output bandwidth;and a receiver having an input band defining an input bandwidth whereina center frequency of the input band of the receiver is variable;wherein the input bandwidth is smaller than the output bandwidth.
 2. Thesystem of claim 1, wherein the audible signal comprises a saw-toothwave.
 3. The system of claim 1, wherein the audible signal has a perioddefining a frequency between about 20 Hz and about 20 kHz.
 4. The systemof claim 1, wherein the audible signal has a period defining a frequencybetween about 60 Hz and about 2 kHz.
 5. The system of claim 1, whereinthe audible signal has a period defining a frequency between about 2 kHzand about 6 kHz.
 6. The system of claim 1, wherein the audible signalcomprises a sequence of audible tones.
 7. The system of claim 1, whereinthe audible signal comprises a sequence of audible tones and pausesbetween the tones.
 8. The system of claim 1, wherein the transmitterfurther includes a battery and the audible signal indicates a conditionof the battery.
 9. The system of claim 1, wherein the transmitterincludes a free running oscillator.
 10. The system of claim 9, whereinthe free running oscillator includes an LC tank circuit having aninductor and a capacitor.
 11. The system of claim 10, wherein theinductor comprises an antenna.
 12. The system of claim 1, wherein thetransmitter further includes a variable capacitance.
 13. The system ofclaim 12, wherein the variable capacitance is provided by a bank ofswitched capacitors.
 14. The system of claim 13, wherein the bank ofswitched capacitors is controlled by an output of a counter.
 15. Thesystem of claim 1, wherein the center frequency of the input band cyclesacross a range of the output band at a sub-audible rate.
 16. The systemof claim 15, wherein the sub-audible rate is between about 0 Hz andabout 10 Hz.
 17. The system of claim 15, wherein the sub-audible rate isbetween about 1 Hz and about 2 Hz.
 18. The system of claim 15, whereinthe input band cycles across the output band following a saw-tooth wavehaving a period defined by the sub-audible rate.
 19. The system of claim15, wherein the input band cycles across only a sub-portion of theoutput band thereby defining a guard band at each end of the outputband.
 20. The system of claim 19, wherein the guard band is at least aswide as the input bandwidth.
 21. The system of claim 1, wherein anoutput bandwidth of the output band is between about 4 MHz and about 5MHz.
 22. The system of claim 1, wherein the input bandwidth is betweenabout 0.1 MHz and about 0.3 MHz.
 23. The system of claim 1, wherein anoutput bandwidth of the output band is between about 4 MHz and about 5MHz and the input bandwidth is between about 0.1 MHz and about 0.3 MHz.24. The system of claim 1, wherein the input bandwidth represents lessthan
 50. % of an output bandwidth of the output band.
 25. The system ofclaim 1, wherein the input bandwidth represents between about 5% andabout 50% of an output bandwidth of the output band.
 26. The system ofclaim 1, wherein the input bandwidth represents between about 2% andabout 8% of an output bandwidth of the output band.
 27. The system ofclaim 1, wherein the receiver includes a detector.
 28. The system ofclaim 27, wherein the detector comprises an AM detector.
 29. The systemof claim 1, wherein the receiver includes an extendable antenna.
 30. Agolf ball comprising: an encapsulated transmitter that modulates anaudible signal to an output band; wherein the output band defines anoutput bandwidth and the transmitter includes a free running oscillatorhaving an inductor and a capacitor.
 31. The golf ball claim 30, whereinthe free running oscillator further has a variable capacitance.
 32. Thegolf ball claim 31, wherein the variable capacitance is provided by abank of switched capacitors.
 33. The golf ball claim 32, wherein thebank of switched capacitors is controlled by an output of a counter. 34.A method to locate a golf ball using a golf ball location system havinga transmitter encapsulated in a golf ball and a receiver, the methodcomprising: modulating an audible signal with the transmitter;transmitting the modulated signal to an output band; providing areceiver with an input band, wherein the input band is narrower andwithin the output band; receiving an input signal residing within theinput band; and varying a center frequency of the input band to traversethe output band.
 35. The method of claim 34, wherein the act of varyingthe center frequency comprises modulating the input band across theoutput band at a sub-audible rate.
 36. The method of claim 34, furthercomprising: extending an antenna on the receiver to increase an inputsignal gain; moving the receiver closer to the transmitter; andretracting the antenna to decrease the input signal gain.
 37. The methodof claim 34, wherein the act of modulating the audible signal comprisescycling a center frequency of the transmitted signal across the outputband at the audible rate.